Fluit compression system control

ABSTRACT

An unloading valve for controlling the capacity of a compressor comprising a housing defining a bore, an inlet to said housing connected to the discharge side of a compressor, a first outlet from said housing connected to the suction side of said compressor, and a second outlet from said housing connected to the discharge manifold of the compressor. Disposed in the bore is a piston assembly and poppet operable in response to changes of pressure in the bore. The piston and poppet move as a result of changes of pressure in the bore, created by the bore being selectively communicated with the side of the compressor and with the discharge side of the compressor. Movement of the piston assembly and poppet selectively communicates the inlet of said valve with either the suction side of the compressor when reduced capacity is required or with the discharge manifold when rated capacity is required.

United States Patent [72] inventor Richard S. Abell Cazenovia, N.Y.

21 AppLNo. 6,621

[22] Filed Jan.28, 1970 Dec. 14, 1971 Carrier Corporation Syracuse, N.Y.

[45] Patented [73] Assignee [54] FLUID COMPRESSION SYSTEM CONTROL [56]References Cited UNITED STATES PATENTS 3,195,319 7/1965 Woltt 3,280,58210/1966 Knachel 62/510 Primary Examiner-Meyer Perlin AnorneysHarry G.Martin, Jr. and J. Raymond Curtin ABSTRACT: An unloading valve forcontrolling the capacity of a compressor comprising a housing defining abore, an inlet to said housing connected to the discharge side of acompressor, a first outlet from said housing connected to the suctionside of said compressor, and a second outlet from said housing connectedto the discharge manifold of the compressor. Disposed in the bore is apiston assembly and poppet operable in response to changes of pressurein the bore. The piston and poppet move as a result of changes ofpressure in the bore, created by the bore being selectively communicatedwith the side of the compressor and with the discharge side of thecompressor. Movement of the piston assembly and poppet selectivelycommunicates the inlet of said valve with either the suction side of thecompressor when reduced capacity is required or with the dischargemanifold when rated capacity is required.

PATENTEBomMen 3, 35,979

SHEET 1 BF 2 INVENTOR. RICHARD s. ABELL ATTORNEY PATENIEBmomnn 3,626,979

sum 2 0F 2 FIG 5 INVENTOR. RICHARD S. ABELL ATTORNEY FLUID COMPRESSIONSYSTEM CONTROL BACKGROUND OF THE INVENTION This invention relates tofluid compressors, and in particular, to an unloading valve operable tocontrol the capacity of such compressors.

In a compressor designed to operate at relatively constant speed, theload on the system in which the compressor is employed may sometimesvary, resulting in inefiicient operation of the compressor unless thecapacity of the compressor may be varied to comply with the systemvariations. For example, constant speed compressors are generallyemployed in refrigeration systems wherein the load on such system mayvary quite substantially.

One of the methods for varying the capacity of a compressor operating atconstant speed is to provide means for bypassing some or all of thecompressors output back to the suction side of the compressor from somepoint in the discharge manifold. One of the methods for obtaining theabove-described reduction of capacity is to employ a valve thatselectively communicates internal passages in the compressor cylinderthat connects the discharge side of the compressor with the suction sidethereof, to provide the desired control of the compressor capacity.Although such a method is efficient, the increased manufacturing costsare undesirable. Secondly, if maintenance is required, increased costsresult due to the unloading device being located internally of thecompressor cylinder. Another method of reducing capacity is to employthree-way valves externally of the compressor, in the dischargemanifold. However, such valves are relatively expensive to manufactureand often require maintenance due to utilization springs which wear, dueto their constant use in such applications.

Additionally, such valves generally create relatively large pressuredrops therethrough and thus do not provide maximum capacity when thecompressor is fully loaded.

The object of this invention is the provision of a three-way valve thatis relatively inexpensive to manufacture, substantially maintenancefree, a.nd one that does not create the excessive undesirable pressuredrops so as to preclude delivery of rated capacity when such isrequired.

SUMMARY OF THE INVENTION This invention relates to fluid compressors,and in particular, to a method and apparatus for controlling thecapacity of the compressor. More particularly, this invention relates tosuch a compressor employed in fluid compression systems including arefrigeration system.

The novel valve herein disclosed provides means to obtain the desiredcapacity control for such compressors. The valve includes a housinghaving an inlet in communication with the discharge side of thecompressor. The valve includes first and second discharge linesextending therefrom, the first line being connected to the suction sideof the compressor, and the second line being connected to the dischargemanifold of the compressor. The valve functions to selectivelycommunicate the discharge side of the compressor with either the suctionside thereof or with the discharge manifold.

The housing of the valve defines a bore. Disposed in the bore ispressure-responsive means including a piston assembly and a poppet.Means associated with the valve selectively communicate the bore witheither the suction side of the compressor when it is desired to operatethe compressor at reduced capacity, or with the discharge side of thecompressor when it is desired to operate the compressor at maximumcapacity. When the bore is in communication with the suction side of thecompressor, the piston and poppet move within the bore so as tocommunicate the inlet of the housing with the suction side of thecompressor and to prevent communication between said inlet and thedischarge manifold. The short circuiting of the refrigerant flow thusobtained effectively reduces the capacity of the compressor when maximumcapacity is not needed, due to a decrease in the load on the system.

When maximum or rated capacity is desired, the bore of the valve isplaced in communication with the discharge side of the compressor. Thepiston assembly and the poppet are thereby moved so as to communicatethe inlet of the valve with the discharge manifold. When compressors ofthe type under discussion are employed in a refrigeration system, thedischarge manifold is connected to the inlet of the condenser of suchsystem.

Although the invention has been discussed as being employed with areciprocating-type compressor, it should be understood that theinvention can be also utilized with other types of fluid compressors,such as centrifugal types, employed in other applications besidesrefrigeration systems.

For example, in applications where a centrifugal compressor is employedto provide pressurized gas, it may be desirable to operate the machineeven though no output therefrom is required, due to there being no loadon the system. During such operation, the invention may be actuated sothat gas discharged from the compressor is vented to the atmosphere orother relatively low-pressure area. Thus, it is apparent that theinvention may readily be utilized with any type of compressor in anypressurized system where it is desirable to vary the output of thecompressor, either totally, as with the centn'fugal compressor, orpartially, as with the reciprocating compressor.

The attached drawings illustrate a preferred embodiment of theinvention.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 schematically shows arefrigeration system illustrating the invention herein disclosed;

FIG. 2 is a cross-sectional view of the novel unloading valve utilizedin the invention illustrating one operating position;

FIG. 3 is a cross-sectional view of the valve in its second operatingposition; and

FIG. 4 is a fragmentary sectional view taken along the line lVlV of FIG.3..

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawings thereis shown the present invention employed in a refrigeration system. Asnoted above, the invention may be employed with compressors utilized inother applications wherein the load on the system may vary. ln referringto the drawings, like numerals shall refer to like parts.

Referring to FIG. 1 there is shown a refrigeration system includingmulticylinder compressor 10 comprising cylinders 11 and 12. Cylinders 11and 12 have extending therefrom discharge lines 13 and 14 respectively;discharge line 14 extends to discharge manifold 24 and line 13communicates cylinder 11 with unloading valve 15. Valve 15 has extendingtherefrom a first discharge conduit 16 and a second discharge conduit23. As will be apparent hereinafter, valve 15 functions to selectivelycommunicate line 13 with either conduit 16 or conduit 23.

Conduit 16 communicates valve 15 with discharge manifold 24. Connectedto the discharge manifold is condenser 17. Line 18 connects the outletof the condenser to the inlet of thermal expansion valve 19, whichfunctions as the refrigerant expansion device. It should be understoodthat other expansion devices, such as capillary tubes may be employed inlieu of expansion valve 19. The outlet of expansion valve 19 isconnected to the inlet of evaporator coil 20 via conduit 18'.

The outlet from evaporator coil 20 is connected to suction manifold 22via conduit 21. Additionally, conduit 23 communicates valve 15 withsuction manifold 22. Suction lines 21' and 22' extend from the suctionmanifold to cylinders 11 and 12, respectively.

In operation, gaseous refrigerant is discharged from compressorcylinders 1 I and 12 via lines 13 and 14. The high-pressure refrigerantgas flowing through line 14 passes to the condenser 17 via dischargemanifold 24.

The gaseous refrigerant flowing through line 13 is either passed tosuction manifold 22 or to discharge manifold 24, depending upon theoperation of valve 15, as will be apparent hereinafter. If rated ormaximum capacity is desired, valve 15 will function to pass'therefrigerant gas to discharge manifold 24 and thence to condenser 17.However, if less than maximum capacity is desired, valve 15 will operateto communicate line 13 with discharge conduit 23 and thence to suctionmanifold 22.

The gaseous refrigerant flowing through condenser 17 is passed in heattransfer relation with a relatively cold medium by means not shownwhereby the cold medium extracts heat from the gaseous refrigerant tocondense same.

The liquid refrigerant thus formed in condenser 17 flows via line 18 toexpansion valve 19 and thence to evaporator 20. The refrigerant flowingthrough evaporator coil 20 passes in heat transfer relation with themedium to be cooled, such as room air, passed thereover by means notshown, whereby the refrigerant extracts heat from the medium to becooled and is vaporized thereby.

The vaporous refrigerant formed in evaporator coil 20 flows to suctionmanifold 22 via conduit 21 and thence to the suction side of cylinders ll and 12 of compressor 10.

In referring now to FIGS. 2 and 3, there is shown a crosssectional viewof the novel valve 15 shown in a loaded position and an unloadedposition, respectively. The novel valve 15 includes a housing 25, whichdefines a cylindrical bore 29. Disposed in bore 29 is piston assembly30, the piston assembly being operable to reciprocally move in the bore.The piston assembly includes stem section 31, which threadably engagesthe upper portion of the piston assembly at 31'.

-Additionally disposed in bore 29 is poppet 32, which also moves in areciprocal manner in the bore. C-ring 28 limits the upward movement ofthe poppet in the bore. Piston assembly includes seal rings 26 and 27,such as O-rings or piston rings, mounted thereon for sealing purposes.

As noted hereinbefore, discharge line 13 communicates the inlet of thevalve with the discharge side of cylinder 11. The gaseous refrigerantthus introduced into bore 29 will be directed by the operation of pistonassembly 30 and poppet 32, as will be apparent hereinafter, to eitherdischarge conduit 16 or discharge conduit 23.

A relatively small bleed line extends from discharge conduit 16 toorifice 39 provided in cap 36. Threadably engaging the lower portion ofcap 36 is end piece 37, which functions to close off the upper portionof bore 29. Orifice 38 in end piece 37 is selectively communicated withorifice 39 in cap 36 and with orifice in cap 36. Orifice 40 is incommunication with discharge conduit 23 via bleed line 34.

Acting to control the communication of orifice 38 with orifices 39 and40 is solenoid-actuated valve 33. As shown in FIG. 2, when full capacityis desired, valve 33 will operate to communicate orifice 39 with orifice38.

As shown in FIG. 3 wherein valve 15 is shown in its unloaded position,solenoid 33 functions to communicate orifice 38 with orifice 40. FIG. 2illustrates solenoid valve 33 in its deenergized position, whereas FIG.3 illustrates solenoid valve 33 in its energized position. A source ofpower represented by lines L and L, controls the energization ofsolenoid valve 33. A switch, not shown, controls the supply of power tosolenoid valve 33. It should be understood that other means may beemployed to selectively communicate the orifices in lieu of solenoidvalve 33.

Referring now to FIG. 3 wherein the novel valve is shown in its unloadedposition, the manner in which the valve operates will hereinafter bedescribed. As noted hereinabove, in the position illustrated by FIG. 3,orifice 38 is in communication with orifice 40. The piston assembly 30is at the highest position within bore 29. Poppet 32 is seated on seat41, thereby preventing flow from line 13 to conduit 16 and communicatingline 13 with conduit 23. Conduit 23, as noted before, communicates withsuction manifold 22 and is, therefore, at suction pressure. Similarly,line 13 is at suction pressure when in communication with conduit 23.Cylinder 11 is thereby prevented from reaching discharge pressure andthe compressor is operated at reduced capacity as desired. The cost ofoperating the compressor at reduced capacity is substantially decreasedsince less power is required by the machine.

When it is desired to deliver rated capacity due to an increase in theload on the refrigeration system, solenoid valve 33 is deenergized sothat communication between orifices 38 and 40 is prevented and orifice38 is placed in communication with orifice 39.

Refrigerant gas at discharge pressure flows from conduit 16 havingcommunication with manifold 24, through line 35 to orifice 39 and thenceto orifice 38 in communication therewith. The lower surface of the stem31 of piston assembly 30 has suction pressure acting thereon. Therefrigerant gas at discharge pressure acting on the top surface ofpiston assembly 30 thus causes the piston assembly to move downwardly inbore 29 so as to prevent communication between line 13 and conduit 23,the poppet 32 and the stem 31 having a sliding fit enabling such actionto obtain.

The refrigerant gas flowing from line 13 through valve 15 fills thespace defined by the upper surface of the stem portion and the lowersurface of the poppet. The pressure therein increases rapidly and veryquickly reaches a magnitude to supply a force to move the poppet in anupward direction in bore 29. The upward movement of poppet 32 is limitedby C- ring 28. When poppet 32 has reached its upper limit of movement,line 13 and discharge conduit 16 are in communication, thus placing line13 at discharge pressure, the parts assuming the position indicated inFIG. 2. Cylinder l 1 thereby operates in its loaded position anddischarges refrigerant gas therefrom at rated discharge pressure.

Assume now that the compressor is operating at rated capacity with thepiston assembly and poppet positioned as shown in FIG. 2. If the load onthe system decreases, it becomes desirable to reduce the capacity of thecompressor to reduce the operating cost thereof and to preventcompressor flooding. To obtain the desired reduced capacity, solenoidvalve 33 is energized so as to communicate orifice 38 with orifice 40.Communication of these orifices causes the refrigerant gas acting on thetop surface of piston 30 to flow from orifice 38 through orifice 40 andbleed line 34 to conduit 23, which is at suction pressure as notedhereinbefore. The refrigerant gas trapped between piston 30 and poppet32, which is substantially at discharge pressure, causes the pistonassembly to begin moving in an upward direction in the bore as thepressure on the upper surface thereof is reduced. It should be notedthat refrigerant gas at discharge pressure is able to pass into thespace between the lower surface of the piston assembly and the uppersurface of the poppet when the valve is in its loaded position as shownin FIG. 2 by leakage around the poppet and through the space of theC-n'ng, as clearly shown in FIG. 4 This space is thus maintained atsubstantially discharge pressure as is desired. The upward movement ofpiston assembly 30 in bore 29 starts to communicate line 13 with conduit23 thereby diverting a portion of the flow of refrigerant gas throughconduit 23 to the suction manifold and, additionally, reducing thepressure acting on the lower surface of poppet 32.

The reduced pressure lessens the force acting on the lower surface ofpoppet 32, and thereby creates a force acting on the poppet, whichcauses the poppet to move downwardly in the bore and to thus sit on seat41. Poppet 32, when seated, prevents any flow of refrigerant gas fromline 13 to conduit 16 and diverts all of the flow of refrigerant gas toconduit 23. Additionally, discharge pressure is maintained in bore 29,via the small passageway 42 shown in FIG. 3, provided between the topportion of the poppet and the housing. The passageway permits leakage ofrefrigerant gas from discharge conduit 16 back into the bore. Thedischarge pressure acts on the lower portion of the piston assembly andcauses the piston assembly to move upward in bore 29 to its maximumposition as shown in FIG. 3.

it is, therefore, readily apparent that the novel valve herein disclosedreadily permits rapid and efficient reduction in compressor capacitywhen desired, and in addition, obviates the repair and manufacturingcost problems of the prior art. Additionally, the relatively largediameter conduits extending from valve and the absence of restrictionsin the bore thereof, reduce the pressure drops therethrough as isdesired to obtain rated capacity when required.

While I have described and illustrated a preferred embodiment of myinvention, it will be understood that the invention is not limitedthereto but may be otherwise embodied within the scope of the followingclaims.

I claim:

1. An unloading valve for controlling the capacity of a fluid compressorcomprising:

A. a housing;

B. inlet means to said housing;

C. first discharge means from said housing;

D. second discharge means from said housing;

E. pressure-responsive means disposed in said housing having a firstoperating position when the fluid compressor is functioning at ratedcapacity and having a second operating position when said fluidcompressor is functioning at reduced capacity, said pressure-responsivemeans communicating said inlet means and said first discharge means whenin its first operating position, and communicating said inlet means withsaid second discharge means when in its second operating position, saidpressure-responsive means including:

1. piston means reciprocally disposed in said valve housing; and

2. poppet means reciprocally disposed in said valve housing, themovement thereof being in an opposite direction to the movement of saidpiston; and

F. means operable to vary the pressure acting on saidpressure-responsive means, said pressure being of a first magnitude whenit is desired to have said pressure-responsive means in its firstoperating position, and being of a second magnitude when it is desiredto have said pressureresponsive means in its second operating position.

2. The unloading valve in accordance with claim 1 wherein said pistonassembly includes a piston portion and a stern portion and wherein saidpoppet means is mounted about said stem portion to move relativethereto.

3. A method of operating an unloading valve for controlling the capacityof a compression mechanism comprising the steps of:

A. selectively communicating the bore of said unloading valve with thedischarge side of said compression mechanism when it is desired tooperate at rated capacity, and with the suction side of said compressionmechanism when it is desired to operate below rated capacity;

B. moving a piston reciprocally disposed in the bore of said valve in anupward direction in said bore when said bore is in communication withthe suction side of said compression mechanism and moving said piston ina downward direction in said bore when said bore is in communicationwith the discharge side of said compression mechanism; and

C. moving a poppet disposed in said bore in an opposite direction to themovement of said piston, said poppet and piston acting in conjunctionwith each other to communicate the inlet of said valve with the inlet ofsaid compression mechanism when said bore is in communication with thesuction side of said compression mechanism, and communicating the inletof said valve to the discharge side of said compression mechanism whensaid bore is in communication with the discharge side of saidcompression mechanism.

1. An unloading valve for controlling the capacity of a fluid compressorcomprising: A. a housing; B. inlet means to said housing; C. firstdischarge means from said housing; D. second discharge means from saidhousing; E. pressure-responsive means disposed in said housing having afirst operating position when the fluid compressor is functioning atrated capacity and having a second operating position when said fluidcompressor is functioning at reduced capacity, said pressure-responsivemeans communicating said inlet means and said first discharge means whenin its first operating position, and communicating said inlet means withsaid second discharge means when in its second operating position, saidpressure-responsive means including:
 1. piston means reciprocallydisposed in said valve housing; and
 2. poppet means reciprocallydisposed in said valve housing, the movement thereof being in anopposite direction to the movement of said piston; and F. means operableto vary the pressure acting on said pressureresponsive means, saidpressure being of a first magnitude when it is desired to have saidpressure-responsive means in its first operating position, and being ofa second magnitude when it is desired to have said pressure-responsivemeans in its second operating position.
 2. poppet means reciprocallydisposed in said valve housing, the movement thereof being in anopposite direction to the movement of said piston; and F. means operableto vary the pressure acting on said pressure-responsive means, saidpressure being of a first magnitude when it is desired to have saidpressure-responsive means in its first operating position, and being ofa second magnitude when it is desired to have said pressure-responsivemeans in its second operating position.
 2. The unloading valve inaccordance with claim 1 wherein said piston assembly includes a pistonportion and a stem portion and wherein said poppet means is mountedabout said stem portion to move relative thereto.
 3. A method ofoperating an unloading vAlve for controlling the capacity of acompression mechanism comprising the steps of: A. selectivelycommunicating the bore of said unloading valve with the discharge sideof said compression mechanism when it is desired to operate at ratedcapacity, and with the suction side of said compression mechanism whenit is desired to operate below rated capacity; B. moving a pistonreciprocally disposed in the bore of said valve in an upward directionin said bore when said bore is in communication with the suction side ofsaid compression mechanism and moving said piston in a downwarddirection in said bore when said bore is in communication with thedischarge side of said compression mechanism; and C. moving a poppetdisposed in said bore in an opposite direction to the movement of saidpiston, said poppet and piston acting in conjunction with each other tocommunicate the inlet of said valve with the inlet of said compressionmechanism when said bore is in communication with the suction side ofsaid compression mechanism, and communicating the inlet of said valve tothe discharge side of said compression mechanism when said bore is incommunication with the discharge side of said compression mechanism.